The present invention relates to a linear motion device.
EP 1 650 854 B1 makes known a linear motion device. According to FIGS. 1 and 2 of EP 1 650 854 B1, linear motion device 10 includes a housing 14 and an arm 12. Two U-shaped guide bodies 24; 25 that enclose the arm are provided in the housing. Four rolling element circuits are located in each of the guide bodies, rolling bodies 40 of which roll on rolling surfaces 64 of arms, which extend in the direction of longitudinal axis V, and therefore the arm is movably guided on the housing, in a direction of longitudinal axis V. The rolling surfaces of the arm are composed of hardened steel, and therefore the guide mechanism has a sufficiently long service life. The motion of the arm relative to the housing is driven via a ball screw drive 18; 20, spindle 20 of which is set into rotation by an electric motor 16. Arm 12 extends via a front end 12a out of housing 12, a separate flange 80 being fastened to front end 12a. 
A related linear motion device is known from the catalog “Feed Moduls VKK” (No. R310EN 2403; version 2008.09) published by the applicant. This linear motion device differs from the linear motion device known from EP 1 650 854 B1, e.g., in terms of the fastening of the flange to the arm. According to page 41 of the aforementioned catalog, a separate, substantially cylindrical receiving peg is provided on the front end of the arm, and includes an external thread that is screwed into the front end of the arm. The separate flange includes a receiving bore that is fitted to the receiving peg. The flange is fastened to the receiving peg using two threaded pins which are screwed into the flange transversely to the longitudinal axis, and so their tip presses against the receiving peg. Using this type of fastening, the flange may be fastened to the arm in any rotary position.
The disadvantage of the flange fastening described above is that it is very difficult to fasten the flange in a defined rotary position relative to the arm. This problem is exacerbated by the fact that the threaded pins plastically deform the receiving peg when they are tightened using the amount of torque required to ensure sufficient clamping. This results in clamping marks being formed in the receiving peg. As a result, it is very difficult to correct small alignment errors once the flange has been tightly clamped to the receiving peg. This is due to the fact that the threaded pins always slide back into the existing clamping marks on the receiving peg if the new clamping position is not sufficiently far away from the clamping marks.